1. Field of the Invention
The present invention relates to an electric vacuum cleaner and particularly to a battery-operated electric vacuum cleaner.
2. Discussion of the Background
As a method of boosting the output of a motor-driven blower of a battery-operated electric vacuum cleaner to thereby enhance dust suction power, there has generally been known a method of increasing power inputted to a motor-driven blower. Described specifically, windings of a motor-driven blower are changed, a current inputted to the motor-driven blower increases, or a source voltage is boosted to thereby increase the input to the motor-driven blower.
When an attempt is made to increase an input current where the motor-driven blower is made up of a commutator motor, carbon at a brush portion brought into contact with a commutator will wear and the motor-driven blower becomes easy to break due to sparks developed in the commutator, whereby it is hard to ensure reliability.
To this end, there is considered a method of boosting a source voltage applied to a motor-driven blower as another method of increasing the power inputted to the motor-driven blower. In the case of a battery-operated electric vacuum cleaner, a method of increasing the number of batteries is the simplest as the method of boosting the source voltage. However, when a high voltage is required, a battery will increase in size when an attempt to realize it by virtue of the battery alone is made. Thus, a method of acquiring a high voltage by using a boost converter circuit has been proposed to solve it. As such an example, there has been known, for example, Unexamined Patent Publication Nos. Hei 8(1996)-224198 and 2001-16845.
In the case of the battery-operated electric vacuum cleaner, the service hour per charge is one of performance important for a user. However, the electric vacuum cleaner is accompanied by a problem that when a boost converter circuit is mounted to the electric vacuum cleaner, the service hour per charge is shortened due to a loss produced upon boosting the voltage by the boost converter circuit.
The invention disclosed in Unexamined Patent Publication No. Hei 8(1996)-224198 is one equipped with a switching means for switching a power supply for supplying power to a motor-driven blower to any one of a commercial source power and a secondary battery. When power is supplied from the secondary battery to the motor-driven blower, a voltage in the power is boosted by a boost converter circuit to drive and-control an AC commutator motor. However, Unexamined Patent Publication No. Hei 8(1996)-224198 does not show a specific disclosure about the relationship between the driving operations of the electric vacuum cleaner and the operation of the boost converter circuit and does not provide suggestions either. Therefore, the electric vacuum cleaner with the secondary battery as a drive source practically involves a demand to reduce power consumption as practicable to thereby make the service hour per charge as long as possible with a view toward lightning cumbersomeness such as a charging operation. On the other hand, Unexamined Patent Publication No. Hei 8(1996)-224198 does not show a solution to such a demand.
In a manner similar to Unexamined Patent Publication No. Hei 8(1996)-224198, Unexamined Patent Publication No. 2001-16845 simply describes that the electric vacuum cleaner is equipped with the boost converter circuit and does not show a specific description indicative of the relationship between the driving operations of the electric vacuum cleaner and the operation of the boost converter circuit. Therefore, Unexamined Patent Publication No. 2001-16845 does not show any solution to the demand to reduce the power consumption as practicable and make the service hour per charge as long as possible for the purpose of lightening the cumbersomeness such as the charging operation, for example.
Particularly when a use form of the electric vacuum cleaner is taken into consideration, a user does not use a cleaner at all times in a state in which power consumption is set to a maximum and dust suction power is kept in the highest state. Therefore, there has been a demand for the provision of an electric vacuum cleaner having functions such as an ability to make long the service hour per charge.
When it is desired to put into practical use an electric vacuum cleaner equipped with a boost converter circuit with a DC power supply as a drive source, it is necessary to take into consideration, for example, avoidance of abnormal conditions of the electric vacuum cleaner incident to the operation of the boost converter circuit, protection of a battery and respective constituent electronic components against the operational malfunction of the boost converter circuit, an influence on the motor-driven blower at the operation of the boost converter circuit, and the relationship between the operation of the boost converter circuit and dust suction power, etc.
However, while Unexamined Patent Publication No. Hei 8(1996)-224198 has described that upon boosting, a boost voltage gradually rises from a low voltage to a predetermined voltage, the present publication does not show items required upon putting into practical use the electric vacuum cleaner equipped with the boost converter circuit with the DC power supply as the drive source, e.g., any disclosure such as a reduction in power loss involved upon boosting and does not show any suggestions either.
Further, Unexamined Patent Publication No. 2001-16845 does not disclose these technologies either.
An object of the present invention is to hold to a required minimum, a power loss produced due to the mounting of a boost converter circuit in an electric vacuum cleaner equipped with the boost converter circuit with a DC power supply as a drive source.
Another object of the present invention is to reduce in size and weight, an electric vacuum cleaner equipped with a boost converter circuit with a DC power supply as a drive source.
The object of the present invention is achieved by the novel electric vacuum cleaner of the present invention.
According to the novel electric vacuum cleaner of the present invention, a voltage supplied to a motor-driven blower with a DC power supply as a drive source is boosted by a boost converter circuit to thereby increase the output of the motor-driven blower so as to enhance dust suction power. The present invention provides, as operation modes of such an electric vacuum cleaner, an operation mode for boosting power inputted to the motor-driven blower by voltage converting means for boosting a voltage outputted from the DC power supply and thereby supplying power to the motor-driven blower, and an operation mode for deboosting the power inputted to the motor-driven blower by the voltage converting means. Consequently, the power inputted to the motor-driven blower can be boosted only when really required, and a loss in power produced due to the mounting of the voltage converting means can be reduced.